391403993 has 8 divisors (see below), whose sum is σ = 401002056. Its totient is φ = 381888000.

The previous prime is 391403989. The next prime is 391404001. The reversal of 391403993 is 399304193.

It can be written as a sum of positive squares in 4 ways, for example, as 77299264 + 314104729 = 8792^2 + 17723^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 391403993 - 2² = 391403989 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 391403993.

It is not an unprimeable number, because it can be changed into a prime (391403963) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10808 + ... + 29993.

It is an arithmetic number, because the mean of its divisors is an integer number (50125257).

Almost surely, 2^391403993 is an apocalyptic number.

It is an amenable number.

391403993 is a deficient number, since it is larger than the sum of its proper divisors (9598063).

391403993 is a wasteful number, since it uses less digits than its factorization.

391403993 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 41035.

The product of its (nonzero) digits is 78732, while the sum is 41.

The square root of 391403993 is about 19783.9326980254. The cubic root of 391403993 is about 731.4900402889.

The spelling of 391403993 in words is "three hundred ninety-one million, four hundred three thousand, nine hundred ninety-three".